HBsAg, also known as hepatitis B surface antigen, can be detected by radioimmunoassay, enzyme immunoassay and time-resolved immunofluorescence spectrometry. 1. Radioimmunoassay: It is a method to induce competitive inhibition reaction with antibodies by means of isotope-labeled and unlabeled antigen. 2. Enzyme-linked immunoassay (ELISA): It is a special reagent analysis method and a new immunoassay technique developed on the basis of immunoenzymatic technology. 3. Time-resolved immunofluorescence spectrometry time-resolved immunofluorescence analysis: with the help of fluorescent probe labeled with antigen or antibody, a fast pulse light source is taken to excite the sample, and the fluorescence signal after background interference is detected with the help of gated monitoring system. In addition, Hepatitis B is a disease that affects the health of the body, and it is recommended that patients choose the appropriate testing method according to their own situation under the guidance of specialists.